This invention relates to an impact type printer head.
A conventional printer head has a plurality of electromagnetic drive devices to drive drive arms corresponding to a plurality of printing elements which are required to have an uniform response characteristic or a uniform printing characteristic. To this end, in the prior art, the individual parts constituting the electromagnetic drive device must have high machining precision. Therefore, when drive arms are stamped out, they are each adjusted to eliminate its possible warp due to the stamping out. A movable yoke is then fixed to each of the drive arms, and the arms are bent forwardly a predetermined quantity under which condition all the yokes are then polished at their back end surfaces, and all the core pieces are polished so as to have a predetermined surface. These arms are adjusted with high precision so as to be uniform and are then assembled.
Another example is known in which a core opposite to a movable yoke is adapted to be moved by a screw structure, the spacing between the core and the movable yoke is adjusted to equalize the printing characteristic.
However, the above prior art requires high precision-finished parts which require skill to adjust and thereby render the manufacturing cost high. Recently, the number of printing elements have tended to increase gradually. Therefore, it is difficult to adjust all the printing elements with high precision to render the printing characteristics uniform, so that it will take much time and labor for adjustment. In the type in which adjustment is made by rotating the core, the core is required to be cylindrical, so that a coil mounted around this core is limited in shape to a cylinder. As the number of printing elements increases, miniaturization becomes very difficult.
It is therefore an object of this invention to provide a printer head in which the respective printing elements are easily capable of obtaining a uniform drive characteristic.